Brain penetration of neurological disorder drugs such as e.g. large biotherapeutic drugs or small molecule drugs having a low brain penetration, is strictly limited by the extensive and impermeable blood-brain-barrier (BBB) together with the other cell component in the neurovascular unit (NVU). Many strategies to overcome this obstacle have been tested and one is to utilize transcytosis pathways mediated by endogenous receptors expressed on the brain capillary endothelium (blood-brain-barrier-receptor). Recombinant proteins such as monoclonal antibodies or peptides have been designed against these receptors to enable receptor-mediated delivery of biotherapeutics to the brain. However, strategies to maximize brain uptake while minimizing miss-sorting within the brain endothelial cells (BECs), and the extent of accumulation within certain organelles (especially organelles that leads to degradation of the biotherapeutic) in BECs, remain unexplored.
Monoclonal antibodies and other biotherapeutics have huge therapeutic potential for treatment of pathology in the central nervous system (CNS). However, their route into the brain is prevented by the BBB. Previous studies have illustrated that a very small percentage (approximately 0.1%) of an IgG injected in the bloodstream are able to penetrate into the CNS compartment (Felgenhauer, Klin. Wschr. 52 (1974) 1158-1164). This will certainly limit any pharmacological effect due to the low concentration within CNS of the antibody.
It was previously found that the percentage of the antibody that distributes into the CNS could be improved by exploiting BBB receptors (i.e., transferrin receptor, insulin receptor and the like) (see, e.g., WO 95/02421).
Therefore, there is a need for delivery systems of neurological disorder drugs across the BBB to shuttle the drugs into the brain efficiently.
In WO 2014/033074 a blood-brain-barrier shuttle is reported.
In WO 2014/189973 anti-transferrin receptor antibodies and methods of use are reported. It is further reported that targeting a BBB receptor with a traditional specific high-affinity antibody generally resulted in limited increase in BBB transport. It was later found that the magnitude of antibody uptake into and distribution in the CNS is inversely related to its binding affinity for the BBB receptor amongst the anti-BBB antibodies studied. For example, a low-affinity antibody to transferrin receptor (TfR) dosed at therapeutic dose levels greatly improves BBB transport and CNS retention of the anti-TfR antibody relative to a higher-affinity anti-TfR antibody, and makes it possible to more readily attain therapeutic concentrations in the CNS (Atwal et al., Sci. Transl. Med. 3 (2011) 84ra43). Proof of such BBB transport was achieved using a bispecific antibody that binds both TfR and the amyloid precursor protein (APP) cleavage enzyme, β-secretase (BACE1). A single systemic dose of the bispecific anti-TfR/BACE1 antibody engineered using a low-affinity antibody not only resulted in significant antibody uptake in brain, but also dramatically reduced levels of brain Aβ1-40 compared to monospecific anti-BACE1 alone, suggesting that BBB penetrance affects the potency of anti-BACE1 (Atwal et al., Sci. Transl. Med. 3 (2011) 84ra43; Yu et al., Sci. Transl. Med. 3 (2011) 84ra44).
Further a thorough nonclinical safety evaluation of monoclonal antibodies (mAbs) intended for therapeutic application is very important due to the increasing complexity of antibody engineering aspects and the variability induced by the diversity of recombinant production cell systems for generation of antibodies. Furthermore, their complex structure, unique biologic functions and the longer half-lives of mAbs compared with traditional small molecule drugs add to the safety considerations in addition to concerns due to prolonged clinical use of mAbs for the treatment of chronic diseases (Lynch, C. M., et al., mAbs 1 (2009) 2-11; Kim, S. J., et al., Mol. Cells 20 (2005) 17-29).
The overall goal of the nonclinical studies for mAbs is to define the toxicological properties of the mAb in question and provide information for product development. The main objectives of the nonclinical evaluation are (1) identification of target organs for toxicity and to determine whether the toxicity is reversible following the treatment, (2) identification of a safe starting dose for human Phase I clinical trials and subsequent dose escalation schemes, (3) provide information to monitor safety parameters in the clinical trials and (4) provide safety data to support claims on the product label. In order to achieve these goals, both in vitro and in vivo nonclinical studies aimed at defining and understanding the pharmacological properties of the antibody are conducted (Lynch, C. M., et al., mAbs 1 (2009) 2-11; Cavagnaro, J. A., In: Cavagnaro, J. A. (Ed.) “Preclinical safety evaluation of biopharmaceuticals”; Hoboken, N.J.: Wiley 2008; 45-65).
For successful nonclinical safety evaluation of a mAb, the most relevant animal species should be chosen for toxicity testing (Lynch, C. M., et al., mAbs 1 (2009) 2-11; Chapman, K., et al., Nat. Rev. Drug Discov. 6 (2007) 120-126). A relevant species is one in which the antibody is pharmacologically active, the target antigen should be present or expressed and tissue cross-reactivity profile should be similar to humans (Lynch, C. M., et al., mAbs 1 (2009) 2-11; Chapman, K., et al., Nat. Rev. Drug Discov. 6 (2007) 120-126; Subramanyam, M. and Mertsching, E., In: Cavagnaro J. A. (Ed.); Preclinical safety evaluation of biopharmaceuticals. Hoboken, N.J.: Wiley 2008; 181-205; Hall, W. C., et al., In: Cavagnaro, J. A. (Ed.); Preclinical safety evaluation of biopharmaceuticals. Hoboken, N.J.: Wiley 2008; 207-240). Using immunochemical or functional assays, a relevant animal species that expresses the desired epitope and demonstrates a tissue cross-reactivity profile similar to human tissues can be identified (Lynch, C. M., et al., mAbs 1 (2009) 2-11; Hall, W. C., et al., In: Cavagnaro, J. A. (Ed.); Preclinical safety evaluation of biopharmaceuticals. Hoboken, N.J.: Wiley 2008; 207-240). Species cross-reactivity studies, which are useful in this process, involve an immunohistochemical survey of tissues from a variety of species using commercially available multi-species tissue microarrays (Lynch, C. M., et al., mAbs 1 (2009) 2-11; Hall, W. C., et al., In: Cavagnaro, J. A. (Ed.); Preclinical safety evaluation of biopharmaceuticals. Hoboken, N.J.: Wiley 2008; 207-240). Alternatively, evaluation of antibody binding to cells from these animals by flow-activated cell sorting (FACS) is typically more sensitive than immunohistochemical analysis of tissue sections (Lynch, C. M., et al., mAbs 1 (2009) 2-11; Subramanyam, M. and Mertsching, E., In: Cavagnaro J. A. (Ed.); Preclinical safety evaluation of biopharmaceuticals. Hoboken, N.J.: Wiley 2008; 181-205). DNA and amino acid sequences of the target antigen should be compared across species; the homology between species should be determined (Lynch, C. M., et al., mAbs 1 (2009) 2-11; Subramanyam, M. and Mertsching, E., In: Cavagnaro J. A. (Ed.); Preclinical safety evaluation of biopharmaceuticals. Hoboken, N.J.: Wiley 2008; 181-205).
In addition, the biodistribution, function and structure of the antigen should be comparable between the relevant animal species and humans to allow evaluation of toxicity arising from antibody binding of the target antigen, which is referred to as on-target toxicity (Lynch, C. M., et al., mAbs 1 (2009) 2-11; 19,20). Furthermore, strong similarities in target antigen tissue distribution in the animal species and humans make it more likely that target organs of toxicity identified in animals will predict potential toxicities in humans. A lack of similarity in antigen tissue distribution between the animal species and humans does not entirely preclude use of the animal species for toxicity studies, but these differences must be taken into consideration for human risk assessment. As for antigen density or affinity, absolute equivalence between the animal model and humans is similarly not required. Justification for the relevancy of the species selected for toxicity testing should be included in the regulatory submission. If only one species is used for safety evaluation, a summary of experiments that demonstrate the absence of additional relevant species is warranted (Lynch, C. M., et al., mAbs 1 (2009) 2-11).
If the monoclonal antibody intended for a therapeutic use does not have a species cross-reactivity either a surrogate antibody has to be used or a different species for the model. Thus, surrogate antibodies are a potential solution to the limited safety testing possible with humanized monoclonal antibodies with restricted species cross-reactivity. However, there are currently no defined criteria by which a potential surrogate antibody should be judged prior to its use in determining safety issues for the clinical agent (Regulatory Toxicology and Pharmacology Volume 40, Issue 3, December 2004, Pages 219-226).
Thus, to identify an animal model for a particular mAb the above considerations have to made. But nevertheless it is necessary that the mAb in question has a cross-reactivity with the target antigen of the test species. Otherwise even the most suitable test species cannot be used. Therefore, there is the need for mAbs that have no intra-species cross reactivity but an inter-species cross reactivity for its target in human and the species intended for non-clinical trials.
In EP 2 708 560 an antibody specifically recognising transferrin receptor is reported. In FR 2 953 841 antibodies directed against the transferrin receptor and uses thereof for immunotherapy of iron-dependent tumours are reported. In US 2009/162359 bivalent, bispecific antibodies are reported.